I'm surprised Firefox didn't warn me when I went to the page. Hostile teleco/MITM waiting for HTTP traffic are a real-world way that nation states deliver exploits.
It did for Librewolf -- what I moved to from Firefox. Self-Signed certs I'm down with, http I'm not, and never will be for any reason. Plain-text data transmissions have no acceptable reasoning.
They're not useless. And I'm well aware of how MITM attacks work. Any hops along the path from my VPN endpoint to the server unencrypted can be, and are: viewed with plaintext. With a self signed certificate I can choose to accept the certificate or not. I'm not arguing to use them, I'm saying I've moved on from http, which is reasonable for me to do in today's 'get all of their data' age.